Different dimple geometrical configurations with a combination of corrugated tubes and twisted tape are numerically investigated. Water is used as a working fluid for constant heat flux heat transfer conditions at the pipe wall. The dimensionless diameter of the dimples (d/D) used in this study is 0.09, 0.18, 0.27, and 0.36. However, the corrugation configuration diameter is 1 mm. The numerical simulations are carried out at the Reynolds number in the range of 1500-14,000. The outcomes reveal that the friction factor (f) and Nu number are augmented as the dimple diameter increases. The Nu number ratio of 1.25 is found for a dimple pipe tube with a diameter of 4 mm. The numerical outcome presented more mixing, secondary, and vortex produced in the main flow direction and near the pipe wall to the rotating flow induced by twisted tape. Moreover, mixed, secondary vortices and rotational flow originate behind and near the dimple, twisted tape, and corrugation surfaces. These rotational and vortices can promote mixing in flow between the thermal boundary layer and velocity boundary flow layer. So, increase the heat transfer enhancement. The improved pipes with different dimple diameters produce a maximum performance evaluation factor of is more than 1.25. K E Y W O R D S corrugated pipe, dimple configurations, evaluation of thermal performance, heat transfer, twisted tape How to cite this article: Al-Obaidi AR, Alhamid J, Hamad F. Flow felid and heat transfer enhancement investigations by using a combination of corrugated tubes with a twisted tape within 3D circular tube based on different dimple configurations.
To reduce the heat exchanger's costs in a highly competitive industry, thermal performance enhancement of the heat exchangers has successfully gained attention in the last few decades. Among different engineering approaches, the application of the enhanced pipes provides a key solution to improve heat performance. In this paper, the investigation develops a numerical study based on the commercially available computational fluid dynamics codes on the turbulent flow in three-dimensional tubular pipes. Various concavity (dimple) diameters with corrugation and twisted tape configurations are investigated. The study has shown that perforated geometrical parameters lead to a high fluid mixing and flow perturbation between the pipe core region and the walls, hence better thermal efficiency. Moreover, a model of concavity (dimple) with a 4 mm diameter allows the highest heat transfer enhancement among other designs. In addition, the study shows that due to the disturbance between the pipe core region and the pipe wall, the transverse vortices and swirl flow generated are forceful, which leads to better heat transfer enhancement compared with the conventional (smooth) pipes. As the Reynolds number (Re) rises, the mixing flow, secondary, and separation flow extend to become higher than the values in a smooth pipe, allowing a higher value of performance evaluation factor to be achieved for a dimple diameter of 1mm at the low Re values. This study, therefore, shows the promising potential of the enhanced pipes in the heat transfer enhancement of heat exchangers that is crucial in industrial applications to save more energy.
The flow characteristics pattern and heat performance improvement have been analysed by applying the computational method in 3D corrugated configuration tubes. Configuration were carried out with varying geometrical parameters, counting various ring corrugated angle over a tube at several Re range between 4000 and 12000. Computational outcomes in this investigation were validated with available experimental data. Outcomes noted that there was a significant alteration in the behavior of flow structure hence an important rise in pressure losses and enhancement in thermal performance due to using corrugated configurations when compared with the normal plane pipe. By utilizing the latter tube under varying parameters, it produces more turbulence flows, separation, mixing, and more distribution in the boundary flow layer, hence enhancing the thermal flow performance. Furthermore, pressure and Nu were augmented when corrugated configurations rise. Besides, these configuration parameters have a significant impact on the value of overall heat performance. Then the higher value was about larger than 1.65. Computational calculations can provide good results on fluid structure inside the pipe and heat transfer augmentation.
Using passive devices are an efficient method to enhance streamline behavior when liquid flows through the circular pipe. The interrupted structure groove is usually used to change the flow patterns. In this analysis, a heat performance numerical technique is applied to study the characteristics of fluid flow and heat transfer of the circular pipe using different axial groove geometrical configurations with different axial groove numbers, including 2, 3, and 4, under different conditions. The number of annular grooves and circumferential positions are the important parameters to analyse with varying operating conditions, with the Reynolds number (Re) range from 1500 to 23,000. A three-dimensional coordinate pipe system is applied using tetrahedron grids. The discretization equations are obtained by deriving algebraic approximations to integral conservation equations. Results observed that using this type of passive method has a low effect on pressure dope compared to the normal one (smooth pipe). The flow change occurs near and closed to the axial groove parameters. Moreover, the Nusselt number (Nu) value for the groove turbulators was higher than the normal one, about 14.5%-21%. The friction factor (f) value for the groove turbulators was higher than the normal one, were about 7.5%-24%. Most friction losses are caused by dynamical pressure dissipation owing to more viscous losses closed to the wall surfaces. The improvement of heat performance using this type of passing method was more than 1.2%.
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